A Rapid Sterility Method Using Solid Phase Cytometry for Cell-Based Preparations and Culture Media and Buffers

In this article, we demonstrate a rapid sterility testing method for non-filterable cell-based preparations and its in-process control media/buffers. The selected rapid sterility test (RST) in this work is based on the ScanRDI^® system, which detects fluorescently labeled microorganisms with solid-phase cytometry. ScanRDI^® has been chosen due to its sensitivity for detecting viable microorganisms down to one microbial cell with a shorter time to detection compared with the compendial sterility test (CST) method. The RST was validated for a CAR-T cell-therapy product with 4 days of time to detection (TTD) and evaluated for in-process control of media/buffers with real-time detection method success according to USP <1223>, Ph. Eur. 5.1.6, and PDA Technical Report No. 33. The validation parameters included limit of detection and equivalence in routine operations, specificity, robustness, ruggedness, and repeatability. For the validation, a combination of pharmacopoeial ATCC strains as well as in-house isolates were used. In addition, the evaluation study of this RST for in-process control of media/buffers was assessed by performing the limit of detection and equivalence with four representative microorganisms. Where applicable, results were statistically evaluated to demonstrate equivalence and no significant difference of the rapid method as compared with the CST method have been detected. All acceptance criteria have been met, and the solid-phase cytometry technology was successfully validated as an alternative sterility test for cell-based preparations and for its in-process control of media/buffer.